Production of nitriles



Patented Oct. 5, 1948 PRODUCTION OF NITRILES William I. Denton,Woodbury, and Richard B.

Bishop, Haddonfield, N. J., assignors to Socony- Vacuum Oil Company,Incorporated, a corporation of New York No Drawing. Application February1, 1946,

Serial No. 545,012

12 Claims. (Cl. 260-4653) -1 This invention relates to a process forproducing nitrlles, and is more particularly concerned with a catalytictriles from olefinic hydrocarbons.

N itriles are organic compounds containing combined nitrogen. Theirformula may be represented thus: RCEN,-in which R is an alkyl or an arylgroup. These compounds are very useful since they canbe convertedreadily to many valuable products such as acids, amines, aldehydes,esters, etc.

As is well known to those familiar with the art, several processes havebeen proposed for the preparation of nitrlles. In general, however, allof these processes have been disadvantageous from one or morestandpoints, namely, the rela-- tively high cost of the reactantsemployed and/or the toxic natureof some of the reactants and/or thenumber of operations involved in their ultimate preparation. Forexample, aliphatic nitrlles have been synthesized by oxidizinghydrocarbons to acids followed by reacting the acids thus obtained withammonia in the presence of silica gel. Other methods involve reactingalkyl halides with alkali cyanides, reacting ketones with hydrogencyanide in the presence of dehydration catalysts, etc. Aromatic nitrileshave been synthesized by reacting alkali cyanides with aromaticsulfonates or with aromatic-substituted alkyl halides; by reacting morecomplex cyanldes such as potassium cuprous cyanide, with diazoniumhalides; by reacting isothiocyanates with copper or with zinc dust; andby reacting aryl aldoximes with acyl halides.

We have now found a process for producing nitrlles which is simple andinexpensive, and which employs non-toxic reactants.

We have discovered that nitriles containing at least two carbon atomscan be prepared by reacting olefinic hydrocarbons with ammonia, atelevated temperatures, in the presence of catalytic material containinga molybdenum oxide or a tungsten oxide.

Our invention is to be distinguished fromthe conventional processes forthe production of hydrogen cyanide wherein carbon compounds, such ascarbon monoxide, methane, and benzene, are reacted with ammonia atelevated temperatures in the presence of alumina, nickel, quartz, clays,oxides of thorium and cerium, copper, iron oxprocess for producingniide, silver, iron, cobalt, chromium, aluminum phosphate, etc. Theprocess of the present invention is also to be distinguished from theprocesses of the prior art for the production of amines whereinhydrocarbons are reacted with ammonia at high temperatures, or atlowertemperatures in the presence of nickel.

Accordingly, it is an object of the present invention to provide aprocess for the production of nitrlles containing at least two carbonatoms. Anotherobject is to afford a catalytic process for the productionof nitrlles containing at least two carbon atoms. An important object isto provide a process for producing nitrlles containing at least twocarbon atoms which is inexpensive and commercially feasible; A specificobject is to provide a process for producing nitrlles containing atleast two carbon atoms from olefinic hydrocarbons. Other objects andadvantages of the present invention will become apparent to thoseskilled in the art from the following description.

Broadly stated, our invention provides an inexpensive and commerciallyfeasible process for the production of nitrlles containing at least twocarbon atoms, which comprises reacting an olefinic hydrocarbon withammonia, in the gaseous phase and at elevated temperatures, in thepresence of catalytic material containing a metal oxide selected fromthe group consisting of molybdenum oxides and tungsten oxides.

Generally speaking, any oleflnic hydrocarbon having at least one olefingroup C=C is suitable as the hydrocarbon reactant in the proeess of ourinvention. Ethylene, propylene, butenes, octenes, methyl heptenes,butadienes, pentadienes, ethyl butenes, hexadienes, heptenes,

. .pentenes, etc. may be mentioned by way of nonlimiting examples. Itwill be clear from the discussion of reaction temperatures set forthhereinafter, that many oleflnic hydrocarbons are not present per se whenin contact with ammonia and a catalyst of the type used herein, for manyof them are cracked to related hydrocarbons under such conditions.Nevertheless, all oleiinic hydrocarbons and their hydrocarbondecomposition products, which are in the vapor phase under theherein-defined reaction conditions serve the purpose of the, presentinvention. It is to be understood also, that hydrocarbon mixtures conbeused.

Although any oleflnic hydrocarbon having at least one olefin group maybe utilized in our process, we especially prefer to use those containingup to about ten carbon atoms, and of these, propylene, butenes, andbutadienes are especially preferred.

The proportions of reactants, i. e., oleflnic hydrocarbon having atleast one olefin group and ammonia, used in our process may be variedover a wide range with little efiect on the conversion per pass andultimate yield. In general, the charge of reactants may contain aslittle as 2 mol. per cent or as much as 98 mol. per cent of olefinichydrocarbons. In practice, however, we use charges containing betweenabout 20 mol. per cent and about 90 mol. of olefinic hydrocarbon, andordinarily, we prefer to use charges containing a molar excess ofammonia over the oleflnic hydrocarbon reactant.

We have found that. the catalyst to be used to produce nitrilescontaining at least two carbon atoms, by reacting olefinic hydrocarbonshaving at least one olefin group, with ammonia, are those containing amolybdenum oxide or a tungsten oxide, such as molybdenum sesquioxide(M0203), molybdenum dioxide (M002), molybdenum trioxide (M003),molybdenum pentoxide (M0205), tungsten dioxide (W02) and tungstentrioxide (W03). Therefore, and in the interest of brev-' ity, it must beclearly understood that when we speak of molybdenum oxide or of tungstenoxide herein and in the claims, we have reference to the various oxidesof molybdenum and tungsten. While all of these metal oxides areoperative in the present process, they are not equivalent in theireffectiveness from the standpoint of catalytic activity, tungstendioxide (W02), for example, being far less eifective than molybdenumtrioxide (M003), the latter being the preferred starting catalyticmaterial.

While these metal oxides exhibit different degrees of effectiveness whenused' per se, they generally -Dssess additional catalytic activity whenused in conjunction with the well known catalytic supports, such asalumina, silica gel, carborundum, pumice, clays and the like. Weespecially prefer to use alumina (A1203) as a catalyst support, and wehave found that a catalyst comprising a molybdenum oxide supported a onalumina is particularly useful for our purpose.

Without any intent of limiting the scope of the present invention, it issuspected that the enhanced catalytic activity of the supportedcatalysts is attributable primarily to their relatively large surfacearea.

The concentration of catalytic metal oxide in the supported catalystsinfluences the conversion per pass. In general, the conversion per passincreases with increase in the concentration of catalytic metal oxide.For example, we have found parts by weight of alumina. It is to beunderstood, however, that supported catalysts containing larger orsmaller amounts of catalytic metal oxides may be used in our process.

We have found also that in order to obtain initial maximum catalyticefliciency, particularly where the catalytic material comprises thehigher catalytic metal oxides, that the catalysts should be conditionedprior to use in the process. As defined herein, conditioned catalystsare those which have been exposed to ammonia or hydrogen, or both, for aperiod of time, several minutes 7 to several hours, depending upon thequantity, at

that a catalyst comprising 20 parts by weight of molybdenum trioxide on80 parts by weight of alumina is more effective than one comprising 10parts by weight of molybdenum triox de Q3! 9 temperatures varyingbetween about 800 F. and about 1300" F. However, if desired, theconditioning treatment may be dispensed with inas much as the catalystbecomes conditioned during the initial stages of our process when thecatalyst comes in contact with the ammonia reactant.

In operation, the catalysts become fouled with carbonaceous materialwhich ultimately affects their catalytic activity. Accordingly, when theemciency of the catalyst declines to a point where further operationbecomes uneconomical or disadvantageous from a practical standpoint, thecatalyst may be regenerated, as is well known in the art, by subjectingthe same to a careful oxidation treatment, for example, by passing astream of air or air diluted with flue gases over the catalyst underappropriate temperature conditions and for a suitable period of time,such as the same period of time as the catalytic operation. Preferably,the oxidation treatment is followed by a purging treatment, such aspassing over the catalyst a stream of purge gas, for example, nitrogen,carbon dioxide, hydrocarbon gases, etc.

The reaction or contact time, i. e., the period of time during which aunit volume of the reactants is in contact with a unit volume ofcatalyst, may vary between a fraction of a second and several minutes.Thus, the contact time may be as low as 0.01 second and as high as 20minutes. We prefer to use contact times varying between 0.1 second andone minute, and more particularly, contact times varying between 0.3

second and 30 seconds.

In general, the temperatures to be used in our process vary betweenabout 800 F. and up to the decomposition temperature of ammonia (about12504300 F.), and preferably, temperaally speaking, the highertemperatures increase the conversion per pass but they also increase thedecomposition of the reactants, thereby decreasing the ultimate yieldsof nitriles. Accordingly, the criteria for determining the optimumtemperature to be used in any particular operation will be based on thenature of the olefinic hydrocarbon reactant, the type of catalyst, and aconsideration of commercial feasibility from the standpoint of strikinga practical balance between conversion per pass and losses todecomposition.

The process of the present invention may be carried out atsubatmospheric, atmospheric or superatmospheric pressures.Superatmospheric pressures are advantageous in that the unreacted chargematerials condense more readily. Subatmospheric pressures appear to,favor the reactions involved since the'reaction products have a largervolume than the reactants, and hence, it is evident from the law of LeChatelier-Braun that the equilibrium favors nitrile formation more atreduced pressures. However, such pressures reduce the throughput ofthereactants and present increased diiilculties in recycling unreactedcharge materials. Therefore, atmospheric pressure or superatmosphericpressures are preferred.

At the present time, the reaction mechanism involved in the process ofthe present invention is not fully understood.v Fundamentally, thesimplest possible method of making nitriles is to introduce nitrogendirectly into the oleflnic hydrocarbon molecule, thereby avoidingintermediate steps with their accompanying increased cost. In ourprocess, we have noted that considerable amounts of hydrogen areevolved: thatwhen olefinic hydrocarbons higher than ethylene areemployed, that aliphatic nitriles having fewer car. bon atoms than theoleflnic hydrocarbon reactant predominate in the reaction product andthat when olefinic hydrocarbons containing at least six carbon atoms areemployed, that allphatic nitriles as well as aromatic nitriles areobtained. Hence, it is postulated, without any intent of limiting thescope of the present invention, that in our process, the aliphaticnitriles are formed in accordance with the following equations, usingpropylene as an example:

and that when oleflnic hydrocarbons containing at least six carbon atomsare employed. the allphatic nitriles are formed in accordance with theforegoing equations, while the aromatic nitriles are formed throughcyclizationv of the olefinic hydrocarbon reactant followed by theintroduction of nitrogen therein.

The present process may be carried out by making use of any of thewell-known techniques for operating catalytic reactions in the vaporphase eflectively. By way of illustration, propylene and ammonia may bebrought together in suitable proportions and the mixture vaporizedin apreheating zone. The vaporized mixture is then introduced into-areaction zone containing a catalyst oi the type defined hereinbefore.The reaction zone may be a chamber of any suitable type useful incontact-catalytic operations; for example, a catalyst bed contained in ashell, or a shell through which the catalyst flows concurrently, orcountercurrently, with the reactants. The vapors of the reactants aremaintained in contact with the catalyst at a predetermined elevatedtemperature and for a predetermined-period of time, both as set forthhereinbefore, and the resulting reaction mixture is passed through acondensing zone into a, receiving chamber. It

will be understood that when the catalyst flows concurrently, orcountercurrently, with the reactants in a reaction chamber, the catalystwill be thereafter suitably separated from the 'reaccondensed in passingthrough the condensing zone and will be retained in the receiving cham-.bar. The aliphatic nitriles can be separated from each other by anycrime numerous and well known separation procedures, such as fractionaldistillation. Similarly, the uncondensed hydrogen the unchangedpropylene, and unchanged ammonia can be separated from each other byacid scrubbing, etc. The unchanged propylene and ammonia can berecycled, with or without fresh propylene and ammonia. to the process.

It will be apparent that the process may be operated as a batch ordiscontinuous process as by using a, catalyst-bed-type reaction chamberin which the catalytic and regeneration operations alternate. With aseries of such reaction chambers, it will be seen that as the catalyticoperation is taking place in one or moreoi the reaction chambers,regeneration oi the catalyst will be taking place in one or more of theother reaction chambers. correspondingly, the process may be continuouswhen we use one or more catalyst chambers through which the catalystflows in contact with the reactants. In such a continuous process, thecatalyst will flow through the reaction zone in contact with thereactants and will thereafter be separated from the reaction mixture as,for example, by accumulating the catalyst on a suitable filter medium,before condensing the reaction mixture. In a continuous process,therefore, the catalystfresh or regenemitted-and the reactants-fresh orrecycle-will continuously flow through a reaction chamber.

The following detailed examples are for the purpose of illustratingmodes of preparing nitriles in accordance with the process of ourinvention, it being clearly understood that the invention is not to beconsidered as limited to the specific olefinic hydrocarbon reactants orto the specific catalysts disclosed therein or to the manipulations andconditions set forth in the examples. As it will be apparent to thoseskilled in the art. a wide variety of other oleflnic hydrocarbons andother catalysts of the type described hereinbef-ore maybeused.

A reactor consisting of a shell containing a catalyst chamber heated bycirculating a heating transfer medium thereover, and containing 100parts by weight of catalyst comprising 10 parts by weight-of molybdenumtrioxide supported on parts by weight of activated alumina was used. Thecatalyst was prepared by soaking commercial activated alumina in anaqueous solution of ammonium molybdate, followed by heating of the thustreated alumina to drive off ammonia and water. The catalyst wasconditioned by passing a stream of ammonia thereover for 45 minutesat900 F. Ammonia and an oleflnic hydrocarbon were introduced in thevapor phase into the reactor. The reaction mixture was passed from thereactor, through a condenser, into a first re-.

separated by distillation. For convenience, the

pertinent data oi. each run are set forth in the following table?reacting propylene with ammonia, in vapor phase,

Example No. it 1 2 3 4 Olellnio Hydrocarbon Reaetant. Propylen EthylenButadiana Butadiene. Mol Ratio: Ammonia to Oleflnlc Hydrocarbon Beaetau3: 1 2: I z; 1 a; 1, Temperature, '1 900 86 995 995. Contact Time,Seconds L l.2-- 1.2. 1.2.

Products 1. Aoetonitrile ,1. Aoetoultrila 1. Aeetonltrile 1.Acetonitrilc Yl ld enpass, Per Cent Weight Based on Olefinlc Hydrocarbon32 25 4 1o,

on an 2. Propionitrilo 2. Butyronitrile Yield per pass... Tm 1.0.

- 3. Propionitrile It will be apparent that the present'inventionprovides an efllcient, inexpensive and saie process for obtainingnitriles. Our process is or considerable value in making availablerelatively inexpensive nitriles which are useful, for example, asintermediate in organic synthesis.

This application is a continuation-in-part of copending application,Serial Number 539,033,1iled June 6, 1944, now abandoned.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such variations and modifications are considered to bewithin the purview and soon of the appended claims.

We claim:

l. -A process for the production of nitriles having at least two carbonatoms, which comprises reacting an oleilnic hydrocarbon containing up toabout ten carbon atoms, with ammonia, in vapor phase, at temperaturesvarying between about 850 F. and about 1075 F., in the presence of amolybdenum oxide.

2. A process for the production of nitriles having at least two carbonatoms, which comprises reacting an olefinic hydrocarbon containing up toabout ten carbon atoms, with ammonia, in

vapor phase, at temperatures varying between about 850 F. and about 1075F., in the presence of a molybdenum oxide supported on a catalystsupport.

3. A process for the production of nitriles having at least two carbonatoms, which comprises reacting an olefinic hydrocarbon containing up toabout ten carbon atoms, with ammonia, in vapor phase, at temperaturesvarying between about 850 F. and about 1075 F., in the presence ofmolybdenum trioxide supported on alumina,

4. A process for the production of nitriles having at least twocarbon'atoms, which comprises reacting l m lene with ammonia, invaporphase, at temperatures varying between about 850 1' and about 1075 F.,in the presence of a molybdenum oxide.

5. A process for the production of nitriles having at least two carbonatoms, which comprises reacting propylene with ammonia, in vapor phase,at temperatures varying between about 850 F. and about 1075 F., in thepresence or a molybdenum oxide, supported on a catalyst support.

6. A process for the production of nitriles havv ing at least two carbonatoms, which comprises and about 1075 F., in'the presence of molybdenumtrioxide supported on alumina. v

7. A process for the production of nitriles having at least two carbonatoms, which comprises reacting a butene with ammonia, in vapor phase,at temperatures varying between about 850 F. and about 1075 F., in thepresence of a molybdenum oxide.

8. A process for the production of nitriles having at least two carbonatoms, which comprises reacting a butene with ammonia, in vapor phase,at temperatures varying between about 850 F. and about 1075 F., in thepresence of a molybdenum oxide supported on a catalyst support.

9. A process for the production of nitriles having at least two carbonatoms, which comprises reacting a butene with ammonia, in vaporphase,

at temperatures varying between about 850 F. and about 1075 F., in thepresence of molybdenum trioxlde supported on alumina.

10. A process for the production of nitriles having at least two carbonatoms, which comprises reacting a butadiene with ammonia, in vaporphase, at temperatures varying between about 850 F. and about 1075 F;,in the presence of a molybdenum oxide.

11. Aprocess for the production of nitriles having at least two carbonatoms, which comprises reacting a butadiene with ammonia, in vaporphase, at temperatures varying between about 850 F. and about 1075? F.,in the presence of a molybdenum oxide supported on a catalyst support.

12. A process for the production of nitriles having at least two carbonatoms, which comprises reacting a butadiene with ammonia, in vaporphase, at temperatures varying between about I 850" F. and about 1075"on, m the presence of molybdenum trloxide supported on alumina.

WILLIAM I. DENTON. RICHARD B. BISHOP.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED. STATES PATENTS

